I saw a post on the eBay subreddit from a seller regarding shipping. They looked at the price to ship the item through eBay, popped off to a third party shipper

I saw a post on the eBay subreddit from a seller regarding shipping. They looked at the price to ship the item through eBay, popped off to a third party shipper to price compare- when they came back to eBay it quoted a new lower price.